For now, one of the most popular tools are digital cameras which convert an image into digital image data and store the data in an internal memory, a memory card, and such recording media. The digital cameras are equipped with a solid state imaging device which converts an image into an electric signal. The solid state imaging device includes a semiconductor substrate with plural photodiodes in a matrix arrangement, a light shielding film with openings above each photodiode, and micro-lenses formed above each opening. A light beam coming through an imaging optical system is converged by the micro-lens to pass through the opening, and received by the photodiode which constitutes a pixel.
The micro-lenses are generally made of a highly insulating polymer resin. Therefore, static charges tend to build up on a surface of the micro-lens, attracting foreign matter to the lens surface. Since a top surface of the solid state imaging device has bumps standing out in the shape of the micro-lenses, it is difficult to remove the foreign matter once it is adsorbed. Also, the bumps get smaller as pixels become smaller, and removal of the foreign matter will be more difficult. In view of this, with the aim to prevent adsorption of foreign matter, there is proposed a method to cover each micro-lens with a conductive film to prevent static charge buildup on the micro-lens surface (see, for example, U.S. Pat. No. 6,586,811 corresponding to Japanese Patent Laid-open Publication No. 2002-83948).
However, when introduced to cover the micro-lens as described above, this conductive film may vary in thickness and possibly changes the shape of the micro-lens. As a result, an optical characteristic of the micro-lens changes, and quality and yield of the solid state imaging devices are lowered.